Still synthesis

The Still synthesis, depicted in Scheme 4.24, began with the construction of the fragment that will link the diene ester and the hydroxypentanoic acid. To this end, D-xylose (139) was converted to the dicyclopentyl ketal, which was selectively hydrolyzed, tosylated, and reduced to give the C-6, C-13 synthon 140 (65%). 

A soln. of 2,2-bis(chloromethyl)acetophenone in acetonitrile added dropwise during 0.5 hr. to N-cyclohex-l-enylpyrrolidine, triethylamine, and acetonitrile, stirring continued 1 hr., the solvent removed, first at atmospheric pressure and finally in vacuo, water added to the resulting immonium salt, and stirred 12 hrs. at room temp. -> 3-benzoylbicyclo[3,3.1]nonan-9-one. Y 81%. F. e. s. H. Stetter, K. D. Ramsch, and K. Elfert, A. 1974, 1322 bicyclo[4.n.l]enones cf. W. C. Still, Synthesis 1976, 453 ring closure with 3-chlor-2-enamines cf. Synth. Meth. 31, 838. 

The Kishi synthesis ot monensin teatures allylic conformational analysis to predict stereochemistry of hydroboratlon-oxidations in acyclic systems. The Still synthesis features acyclic diastereoselection in carbonyl addition reactions (chelation control and Felkin-Ahn control). 

The chemical synthesis of carbon-containing molecules has been a very important field of scientific work and endeavor for over a centuiy However, the subject is still far aw ay from being fully developed. One of the major reasons for this is the almost unlimited number of organic structures which can exist as discrete compounds. On the other hand there has been a continuing growth in the ability of chemists to construct increasingly complex molecules. 

The monosubstituted malonic ester still possesses an activated hydrogen atom in its CH group it can be converted into a sodio derivative (the anion is likewise mesomeric) and this caused to react with an alkyl halide to give a C-disubstituted malonic ester. The procedure may accordingly be employed for the synthesis of dialkyImalonic and dialkylacetic acids ... 

Although the CFCs and HCFCs are not as stable as the PFCs, they still can be rather stable compounds (3,11)- Dichlorodifluoromethane, CCI2F2, is stable at 500°C in quartz CCl F and CHCIF2 begin to decompose at 450 and 290°C, respectively (7). The pyrolysis of CHCIF2 at 650—700°C in metal tubes is the basis of a commercial synthesis of tetrafluoroethylene ... 

Alkali Fusion of /u-Benzenedisulfonic Acid. Even though this process like the previous one is a very ancient one, it is still the main route for the synthesis of resorcinol. It has been described in detail previously and does not seem to have drastically evolved since 1980. It involves the reaction of benzene with sulfuric acid to form y -benzenedisulfonic acid which is then converted to its disulfonate sodium salt by treatment with sodium sulfite. In a second step, this salt is heated to 350°C in the presence of sodium hydroxide yielding the sodium resorcinate and sodium sulfite. 

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